jQuery’s $.extend is slow—
Trevor Lalish-Menagh runs some experiments and discovers that $.extend is by far the slowest way to add functions to an object. Assigning methods as anonymous functions is the fastest overall.

Exploring JavaScript for-in Loops—
The for-in statement is the only ECMAScript compliant interface for iterating the properties of generic objects. Angus Croll takes a comprehensive walk through the world of for/in and shows off plenty of examples along the way.

OOP The Good Parts—
Nick Fitzgerald takes us on a tour of the strengths and weaknesses of object oriented programming looking at duck-typing, message passing and composition - all with JavaScript examples.

2010 Through The Lens of YUI Theater—
NetTuts+ rounds up almost 50 videos taken from the Yahoo's YUI Theater project focusing on topics like HTML5, JavaScript, CSS3, node.js, and, more often than not, Yahoo's own technology stack including YUI and YQL.

GammaJS: A WebGL Platformer Game Engine—
GammaJS is a new JavaScript library which can be used to create 2.5D platform games for a web browser using the power of HTML, JavaScript, CSS and WebGL (the 3D canvas-a-like supported by recent builds of Chrome and Firefox 4).

node-scraper: Scraping Web Sites From node.js—
node-scraper is a 'little module [for node.js] that makes scraping websites a little easier.' It uses jQuery. Examples are provided showing off a simple fetch of a single page, moving on to parallel fetching and rate limiting.

Visify.js: Stacked Bar Charts for jQuery—
Visify.js is a jQuery plugin by Daniel Westendorf that creates stacked bar charts (bar charts with two values represented in each bar). Straightforward and the official page has some basic examples.

JavaScript Fractals—
Mounier Florian shows off a simple example of drawing a Newton fractal using JavaScript and Canvas. View source to find the JavaScript responsible or keep reloading to see new patterns.

List of languages that compile to JS—
Jeremy Ashkenas, the creator of CoffeeScript, is maintaining a list of programming languages that compile down to JavaScript. Some interesting projects are in the list so far including some CoffeeScript variants..